<template>
  <div>
    <!-- 无id时, 可以使用index(反正也是就地更新) -->
    <div style="display: inline-block; margin: 0 10px" v-for="(item, i) in arr" :key="i">
      <input type="checkbox" v-model="sumArr" :value="item" :id="i" />
      <label :for="i">{{ item }} </label>
    </div>
    <p>你选中的元素, 累加的值和为: {{ sum }}</p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      arr: [9, 15, 19, 25, 29, 31, 48, 57, 62, 79, 87],
      sumArr: [],
      sum: ''
    }
  },
  // computed: {
  //   sum() {
  //     return this.sumArr.reduce((previousValue, currentValue) => previousValue + currentValue, 0)
  //   }
  // }
  updated() {
    this.sum = this.sumArr.reduce((previousValue, currentValue) => previousValue + currentValue, 0)
  }
}
</script>
